Page Speed Optimization Libraries
1.11.33.2
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#include "lazyload_images_filter.h"
Public Member Functions | |
LazyloadImagesFilter (RewriteDriver *driver) | |
virtual const char * | Name () const |
ScriptUsage | GetScriptUsage () const override |
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CommonFilter (RewriteDriver *driver) | |
const GoogleUrl & | base_url () const |
Getters. More... | |
const GoogleUrl & | decoded_base_url () const |
RewriteDriver * | driver () const |
HtmlElement * | noscript_element () const |
void | InsertNodeAtBodyEnd (HtmlNode *data) |
virtual void | StartDocument () |
Note: Don't overload these methods, overload the implementers instead! | |
virtual void | StartElement (HtmlElement *element) |
virtual void | EndElement (HtmlElement *element) |
virtual void | Characters (HtmlCharactersNode *characters) |
ResourcePtr | CreateInputResource (StringPiece input_url, bool *is_authorized) |
ResourcePtr | CreateInputResourceOrInsertDebugComment (StringPiece input_url, HtmlElement *element) |
void | ResolveUrl (StringPiece input_url, GoogleUrl *out_url) |
bool | BaseUrlIsValid () const |
bool | DebugMode () const |
bool | CanAddPagespeedOnloadToImage (const HtmlElement &) |
virtual void | LogFilterModifiedContent () |
virtual RewriteDriver::InlineAuthorizationPolicy | AllowUnauthorizedDomain () const |
virtual bool | IntendedForInlining () const |
void | AddJsToElement (StringPiece js, HtmlElement *script) |
Static Public Member Functions | |
static void | InitStats (Statistics *statistics) |
static void | Terminate () |
static RewriterHtmlApplication::Status | ShouldApply (RewriteDriver *driver) |
Lazyload filter will be no op for the request if ShouldApply returns false. | |
static GoogleString | GetLazyloadJsSnippet (const RewriteOptions *options, StaticAssetManager *static_asset_manager) |
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static bool | ExtractMetaTagDetails (const HtmlElement &element, const ResponseHeaders *headers, GoogleString *content, GoogleString *mime_type, GoogleString *charset) |
Static Public Attributes | |
static const char * | kImageLazyloadCode |
static const char * | kImageOnloadCode |
static const char * | kLoadAllImages |
static const char * | kOverrideAttributeFunctions |
static const char * | kIsLazyloadScriptInsertedPropertyName |
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static const char | kCreateResourceFailedDebugMsg [] |
Debug message to be inserted when resource creation fails. | |
Additional Inherited Members | |
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ServerContext * | server_context () const |
const RewriteOptions * | rewrite_options () |
virtual const char * | LoggingId () |
Filter to lazyload images by replacing the src with a data-pagespeed-lazy-src attribute and injecting a javascript to detect which images are in the user's viewport and swapping the src back.
This filter only works if the document has a head. It adds some javascript to the head that determines if an image is visible and adds a listener to the window scroll event. If an image is visible, it replaces the src and the data-pagespeed-lazy-src attributes.
In order to immediately load images that are above the fold, we attach an onload event to each image. This onload event determines if the image is visible and immediately replaces the src with the data-pagespeed-lazy-src. Otherwise, the image is added to the deferred queue. Since the onload event is only fired if the image src is valid, we add a fixed inlined image to each image node we are deferring.
When the user scrolls, we scan through the deferred queue and determine which images are now visible, and switch the src and data-pagespeed-lazy-src.
Given the following input html: <html> <head> </head> <body>
</body> </html>
The output will be <html> <head> <script> Javascript that determines which images are visible and attaches a window.scroll event. </script> </head> <body>
</body>